Industrial waste waters commonly include a variety of contaminants which require treatment or removal before the waste water can be discharged. Certain industrial processes, such as mining, generate waste water with oxyanion and/or metal contaminants. Oxyanions are negatively charged inorganic molecules with various degrees of oxidation, for example; COx, SOx, NOx, POx, ClO2, AsOx, SeOx, etc. Metal contaminants are toxic metals that may form poisonous water-soluble compounds, including for example mercury, cadmium, lead, chromium, molybdenum, and barium, among others. Both oxyanion and metal contaminants occur in various concentrations throughout the ecosystem and can be observed in elevated levels following various industrial processes, for example mining processes.
There are various commercial technologies for the removal of contaminants from an aqueous stream, including, for example: adsorption (e.g., adsorption on granular iron based media; adsorption on ion-exchange resins; and adsorption on activated alumina); chemical treatment (e.g., precipitation, cementation, coagulation, and flocculation methods); media filtration (filtering through sand, clay, titanium dioxide, ion exchange resins or membranes such as osmosis or nanofiltration membranes); and biomediated removal. Many of these methods require multiple steps to pretreat or chemically reduce the contamination. Many of these methods generate additional hazardous waste that must be further treated or handled.
The description herein of certain advantages and disadvantages of known methods is not intended to limit the scope of the present invention. Indeed the present embodiments may include some or all of the features described above without suffering from the same disadvantages.